LTE-A (Long Term Evolution-Advanced), an evolution of UMTS (Universal Mobile Telecommunication System), is the largest new project developed by the 3GPP (3rd Generation Partnership Project) over recent years. It has certain features of the fourth generation of telecommunications (4G), and even can be regarded as a “pre-4G” technology. LTE-A improves and enhances the air interface of 3G, using OFDM (Orthogonal frequency-division multiplexing) and MIMO (multiple-input and multiple-output) as the basic technologies of the evolution of wireless network, which can provide a better solution to intra-cell interference, and achieve higher network capacity, faster peak data rate and wider network coverage in comparison with CDMA (Code division multiple access). But these come at the expense of more severe ICI (Inter-Cell Interference) brought by OFDM system than that by CDMA system.
CoMP (Coordinated Multipoint Transmission) is one of the key technologies of LTE-A. It can effectively solve the ICI problem, and increase cell throughput and cell-edge user data rates. FIG. 1 illustrates the joint processing/transmission of CoMP. Data information of a particular user is shared among coordinated cells, and the entire cluster of coordinated cells together serve a user or multiple users, thereby reducing ICI and improving cell-edge user performance. However, in order to implement CoMP, it is necessary for a base station to acquire all the channel information between each of users and the base station within the coordination region. The channel information feedback enables the system to perform precise resource scheduling and good link adaptation, which leads to improved downlink performance. However, the channel information feedback also incurs additional overhead on PUSCH (Physical Uplink Shared Channel), which results in degraded uplink spectral efficiency. Therefore, it is desired to provide a proper feedback scheme to reduce the amount of feedback of the system and improve the system spectral efficiency on the premise that the base station can acquire precise channel information.